The present invention relates to casting resins suitable for the production of fire retardant covers for electrical and electronic devices.
Casting resins can be used to protect active and passive components by covering, embedding, or sheathing the components with the casting resin. To protect the covered components, the hardened casting resin molding compounds should contain as few corrosion-stimulating components as possible. In particular, the casting resin should not contain ionic impurities.
Additionally, in order to reduce the risk of fire, casting resins should be fire retardant. Flammability is always a concern during the operation of electrical and electronic devices. The problem of producing fire retardant casting resin molding components has not been satisfactorily solved.
For example, known casting resins containing inorganic additives such as aluminum hydroxides, magnesium hydroxides, phosphates, borates, or red phosphors, have been used to reduce the risk of flammability. These additives, however, have undesirable effects on the thermal mechanical characteristics of the molding compounds during the resin processing. In particular, they cause an increase in the viscosity and sedimentation of the casting resins.
Other casting resin molding materials contain organic additives to achieve a fire retardant effect. The disadvantage of these additives, for example phosphorus-organic compounds, is that they display migratory characteristics when embedded in the resin matrix. While operating components covered with casting resin molding material containing organic additives, the migratory nature of the additives causes the characteristics of the casting resin molding compounds to fluctuate. The variation of the properties of the resin has an adverse effect on the operation of the components contained therein.
Halogenized, particularly bromized, resin components, to which antimony trioxide is frequently added to synergistically effect other components, provide a good flame retardant. But, in the case of fire, such fire retarding agents release toxic, environmentally contaminating substances. Further, it is preferred to limit the use of antimony trioxide, as it is a carcinogen.